util: polkit: Fix polkit agent startup
util: polkit: Fix polkit agent startup

Commit 0b36b0e9 broke polkit agent startup when attempting to fix a
coverity warning. Refactor it properly so that we don't need the 'cmd'
intermediate variable.

jardasgit/libvirt,nertpinx/libvirt,crobinso/libvirt,jfehlig/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,zippy2/libvirt,andreabolognani/libvirt,olafhering/libvirt,taget/libvirt,eskultety/libvirt,eskultety/libvirt,crobinso/libvirt,datto/libvirt,zippy2/libvirt,crobinso/libvirt,zippy2/libvirt,taget/libvirt,datto/libvirt,jfehlig/libvirt,nertpinx/libvirt,crobinso/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,olafhering/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,datto/libvirt,eskultety/libvirt,andreabolognani/libvirt,taget/libvirt,taget/libvirt,libvirt/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,taget/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,datto/libvirt,zippy2/libvirt,eskultety/libvirt,jardasgit/libvirt,libvirt/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,eskultety/libvirt,andreabolognani/libvirt,datto/libvirt,jfehlig/libvirt,libvirt/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt